1.Field of the Invention
This invention relates to a motor driving device used for driving a motor in the forward and reverse direction.
2.Description of the Prior Art
Heretofore, there have been known various types of motor driving devices having different circuit formation. One of them has circuit formation shown in FIG. 2 for example.
A motor driving device 101 shown in FIG. 2 has circuit formation comprising a switching part Ql for supplying a current in the forward rotational direction to a motor 102 which is rotatable in the forward and reverse direction, a switching part Q2 for supplying said motor 102 with a current in the reverse rotational direction, a switching part Q3 for grounding the current in the forward rotational direction through the motor 102, a switching part Q4 for grounding the current in the reverse rotational direction through the motor 102, diodes Dl to D4 for protecting said respective switching parts Ql to Q4 from back electromotive force and detection parts 103 and 104 connected with both terminals of said motor 102 for detecting rotational conditions of said motor 102. The respective switching parts Ql to Q4 are connected with both terminals of said motor 102 in H-bridge connection (hereupon, respective switching parts Q1 to Q4 are indicated with equivalent circuits).
Said motor driving device 101 is so designed as to drive the motor 102 in the direction of forward or reverse rotation by turning on or off the respective switching parts Q1 to 04 according to instructions from a microcomputer for example, and to detect conditions of the motor 102 using the microcomputer through the detection parts 103 and 104.
However, in the conventional motor driving device 101 described above, it is merely possible to detect a breakdown of either switching parts Ql, Q2 or Q3, Q4 because rotational conditions of the motor 102 are detected by the detection parts 103 and 104 when the switching parts Ql to Q4 break down by open breakage or short breakage. There is a problem since it is not possible to detect all conditions of the switching parts Q1 to Q4.